#include<cstdio>//uncle-lu
#include<algorithm>
template<class T>void read(T &x)
{
	x=0;int f=0;char ch=getchar();
	while(ch<'0'||ch>'9') { f|=(ch=='-'); ch=getchar(); }
	while(ch<='9'&&ch>='0') { x=(x<<1)+(x<<3)+(ch^48); ch=getchar(); }
	x = f ? -x : x;
	return ;
}

int w[10010], v[10010];
int F[10000010];
int t, m;

int main()
{
	read(t);
	read(m);
	for (int i = 1; i <= m; i++)
	{
		read(v[i]);read(w[i]);
	}

	for (int i = 1; i <= m; i++) 
		for (int j = v[i]; j <= t; j++) 
			F[j] = std::max(F[j], F[j-v[i]]+w[i]);

	printf("%d", F[t]);
	return 0;
}
